1. Field of the Invention
The present invention relates to sensor sheet suitably used for measuring distribution of force applied from outside.
2. Description of the Related Art
Sensor sheet which is capable of measuring distribution of force applied from outside is in use for analysis of a person's walking manner, for example. In general, the sensor sheet comprises a PET film on which a swath of pressure-sensitive resistance ink is printed along a longitudinal direction thereof and a PET film on which a swath of pressure-sensitive resistance ink is printed along a horizontal direction thereof (a direction orthogonal to the longitudinal direction) which are laminated so that the respective pressure-sensitive resistance inks are intersected with each other. In this sensor sheet, when a force is applied to the sensor sheet from outside, the sensor sheet changes in contact resistance between the two PET films at the force-applied place. By detecting temporal changes of magnitude of the contact resistance along lines of pressure-sensitive resistance ink, distribution of the force (pressure) applied from outside can be measured.
However, this sensor sheet can only measure a distribution of a one-dimensional force applied from outside for a vertical direction of the sensor sheet. When a force of an oblique direction (any direction but a vertical direction) with respect to the sensor sheet is applied to the sensor sheet, the sensor sheet can only measure distribution of force corresponding to a component of the force of the oblique direction acting in a vertical direction to the sensor sheet and having magnitude for the vertical direction. Thus, the conventional sensor sheet cannot make a thorough analysis of distribution of force applied from outside in different directions.